Diffusion in gases
2 marks · EasyExplain, using the particle model, why diffusion happens faster in a gas than in a liquid.
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Particles in a gas move much faster and are further apart, so they can spread out and mix more quickly. In liquids, particles are closer together and move more slowly, so diffusion is slower.
Also accept: Gas particles have more energy and move more freely than in a liquid, so they diffuse quicker.
Common mistakes: Just stating that diffusion is faster without mentioning particles.; Saying gases are lighter (without explaining speed/spacing).
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Marking points
M1 · 1 mark · States that in gases particles move faster/have more energy/are more free to move.
A1 · 1 mark · States that particles are further apart in gases (or closer together in liquids), allowing quicker spreading.
Worked solution
In a gas, particles move very quickly and are far apart, so they mix and spread out faster. In a liquid, particles move more slowly and are closer together, slowing down diffusion.